1. Field of the Invention
The present invention relates to a collision judging system for a vehicle.
2. Description of the Prior Art
A collision preventing system is conventionally known as disclosed, e.g., in Japanese Patent Publication No. 4700/86, in which a distance between the subject vehicle and an objective obstacle is measured, while at the same time, a slip distance for braking at a current travel speed of the subject vehicle, is calculated, and both the distances are compared with each other, whereby a brake device is operated on the basis of the result of comparison.
However, the calculated slip distance for braking is relatively long, even on a travel road surface having a large friction coefficient. Therefore, the brake device is operated, even if there is enough distance for avoiding the collision by steering operation, resulting in a high frequency of operation of the brake device, which is not preferred for the driver's feeling of driving operation. If a variation in friction coefficient of the travel road surface is taken into consideration, the timing of starting the braking operation becomes early, resulting in a further significantly increased frequency of operation of the brake device and in a further significantly deteriorated feeling of driving operation.